The present invention relates to an exchangeable tape unit to be assembled in a tape cassette and in which a heat sensitive printing tape is wound over a tape spool, and more particularly, to such tape unit in which heat sensitive coloring layer of the heat sensitive printing tape is positioned radially inwardly when winding the tape over the tape spool.
Conventionally, a tape cassette used for a tape printer accommodates therein a printing tape on which characters etc. are printed by means of a thermal head etc. When the printing tape is used up, a new roll of a printing tape is exchangeable with the used-up roll. Various proposals have been made on such tape cassettes by the applicant. The exchange of the printing tape is generally achieved by exchanging the tape spool and the tape wound thereover as one unit on the tape cassette.
Further, in the conventional tape printer, a thermal head is positioned outside of the contour of the tape cassette. The thermal head is generally adapted for printing an image on an image receiving medium such as a paper by selectively heat-driving a plurality of heat generating elements.
For printing the image on the tape, the heat generating elements of the thermal head are in contact with the outer side of the printing tape fed from the tape cassette. Accordingly, the heat sensitive coloring layer of the printing tape is generally positioned radially outwardly in an exchangeable roll of the tape wound over the tape spool.
However, in the above described conventional exchangeable tape roll, the heat sensitive coloring layer is exposed to outside, since the printing tape is wound over the tape spool in such a manner that the heat sensitive coloring layer is positioned radially outwardly in the resultant roll. Regarding the tape cassette, it provides a window for visually acknowledging a remaining amount of the tape. Thus, light easily enters the interior of the tape cassette through the window. Moreover, various kinds of the printing tapes are prepared in terms of width and color, etc. A user may exchange the tape roll with another kind of the tape roll even if the tape roll has not yet been used up. Thus, the removed tape roll is exposed to light unless it is stored in a dark place.
The heat sensitive coloring layer is very likely affected by external light, heat, etc. Accordingly, if the heat sensitive coloring layer of the printing tape is exposed to outside, color change and quality change may occur in the exposed portion of the layer. Therefore, storage of the exchangeable tape and the spool incurs difficulty, and printing quality may be degraded unless the tape is stored in a severe condition.
If the printing tape is exposed to external light, heat, etc., a boundary is generated between the color changed zone and unchanged zone in the heat sensitive coloring layer. Further, the heat sensitive coloring layer generates color when frictionally contacting with other article. Thus, the exchangeable printing tape roll whose heat sensitive coloring layer is exposed to light, etc. may excessively lower the sales value.